1. Technical Field
Example embodiments herein relate to wireless communication systems, and more particularly, to sidelink operations in User Equipments (UEs) of the wireless communication systems.
2. Description of the Related Art
Third Generation Partnership Project (3GPP) standard for wireless communications has introduced availability of Proximity based Services (ProSe) in Long Term Evolution (LTE) Release-12. This enables cellular networks such as the LTE network to utilize broadband communication technology for public safety networks. To enable ProSe, sidelink operations are defined in 3GPP that enable User Equipments (UEs) in proximity to directly communicate with each other using RF resources allocated to the UE. The ProSe can be used for multiple tasks including mission critical operations or activities such as public safety, as well as for general services (e.g., social networking and/or targeted advertisement). The ProSe enables reducing data load on cellular networks. The ProSe implementation enables the UE to initiate sidelink operations as defined in the 3GPP specification for communicating with UEs in proximity. The sidelink transmission is designed to use the existing uplink hardware of the UE. Any UE registered for sidelink feature can initiate the sidelink procedure and perform device discovery and communication in accordance with the current 3GPP specification.
However, for a UE with multi Subscriber Identity Module (SIM) multi standby operation (for example, a Dual SIM Dual Standby (DSDS) UE), where the Radio Frequency (RF) resources of the UE are shared between the multiple SIMs of the UE, the current sidelink procedures defined in the 3GPP standard may not provide clarity on procedures to be followed in typical scenarios. For example, consider a scenario where a SIM 1 of the DSDS UE, which is registered for the ProSe services, loses network coverage of its network operator 1 due to emergency such as fire in the building. Currently, as per the defined 3GPP specification the UE may initiate the sidelink operations on SIM 1. Further, in the DSDS scenario, the UE is supposed to share the RF resources between the SIM 1 and SIM 2 of network operator 2. Thus, even though sidelink operations may be triggered on SIM 1, as per the standard RF resources sharing procedures of DSDS UEs, the RF is allotted to the SIM 2 for reception of any paging sequence on SIM 2. If the paging sequence is received, the UE may switch to network operator 2. Thus, the sidelink operations triggered on SIM 1 may be held up till the UE allots the RF resources back to SIM 1. Thus, sidelink procedures that are initiated on SIM 1 for mission critical activity (public safety measure) may get delayed according to the current standards. Such a delay is undesirable, and/or may be prove fatal in mission critical activities (e.g., building on fire, earthquake, or cyclone). Moreover, in mission critical activity, a quick communication with any UE in proximity is desired. For sidelink operation to work, new channels such as Sidelink Broadcast Channel (SL-BCH), Sidelink Discovery Channel (SL-DCH) and Sidelink Shared Channel (SL-SCH) are defined by the 3GPP specifications. For public safety feature (mission critical activity) to work effectively using sidelink in DSDS scenario, a comprehensive usage of the RF is desired for broadcast and/or shared channel usage.